Field of the Invention
The present invention relates to an image forming apparatus forming an image on a sheet.
Description of the Related Art
Hitherto, there is known an electro-photographic image forming apparatus such as a copier, a facsimile, and a laser printer that forms images on a first surface, i.e., a front surface, of a sheet and also on a second surface, i.e., a back surface of the sheet. In forming the images on the both surfaces of the sheet, such image forming apparatus forms a toner image on a photosensitive drum and transfers the toner image onto the first surface of the sheet, supplied from a sheet feeding portion, at a transfer portion.
Then, after fixing the toner image transferred onto the sheet as a permanent image by a fixing portion provided downstream of the image forming portion, the image forming apparatus conveys the sheet to a reverse portion. Then, the image forming apparatus conveys the sheet whose front and back surfaces are reversed by the reverse portion to the image forming portion again to form the image on the second surface of the sheet.
Here, the sheet is being heated to a predetermined temperature during a fixing process of fixing the toner image onto the sheet in the image forming apparatus, and due to the heat, there is a case when moisture contained in the sheet evaporates as vapors.
Therefore, there is a case that dew condensation occurs on a conveyance rollers due to the vapors generated from the sheet heated by the fixing portion. Then, if the dew condensation occurs, the moisture adheres on the sheet passing through the conveyance rollers. Then, there is a possibility that the moisture causes a defective image, conveyance failure, stain of the sheet or the like.
Then, Japanese Patent Application Laid-open No. 2013-257383 proposes an image forming apparatus including a fan blowing air to prevent the dew condensation. However, the image forming apparatus disclosed in Japanese Patent Application Laid-open No. 2013-257383 requires a fan large enough to prevent the dew condensation.